It is known that four of the five species of the Panthera genus, the exception being the snow leopard, P. uncia, can hybridize with each other to produce numerous hybrids. Most hybrids would not survive in the wild due to the males being infertile, but a few (such as the Leopon) are fertile and have a chance of survival in the wild. However, recent mitochondrial genome research by Texas A&M University geneticist William Murphy et al reveals that wild hybrids did also occur in ancient times. In snow leopards and lions, the mitochondrial genomes of both species was more similar to each other than to other Panthera species, indicating that at some point in their history, the female progeny of the male ancestors of modern snow leopards and female ancestors of modern lions interbred with male ancestors of modern snow leopards.